When I use lock screen with ubuntu 12.04, all applications are hidden and a simple window asks me to enter my password to unlock the screen. After a while of inactivity, the screen goes black. However, only a few seconds after, it goes back to that window again as though the mouse had been moved, though that is not the case. Is this a known bug, and if so, how to get around it, and if not, then what I am doing wrong ?

Yes I do have that feature on. This indeed helps, thank you very much. Would you care to elaborate why it is an issue, and how to make it disappear, if you know how ?
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NaomiJOSep 15 '12 at 1:44

(I think that you can edit your own post, in case you can't add a comment).
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NaomiJOSep 15 '12 at 1:56

Please don't let me hanging after such a great (yet incomplete) answer :(. I think you pointed out the problem, but I'm yet to understand why it is a problem, and how to fix it
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NaomiJOSep 15 '12 at 5:04

Well in some cases the motherboard bios could be to new for the kernel to realize it's there, others could be that development never happened for it and the kernel doesn't know how to handle it when it wakes up. In any case WOL is used to keep a machine alive for things of this nature - db transactions or some client server activity. I personally don't like wol but there are cases where it is necessary.

As for a fix I think if you turn WOL off that would fix your problem as to why it causes it. I am not sure. I am sorry if that is not a complete answer, I will try and research it for you as best I can.

WOL (wake on lan), as its name suggests, allows to start a computer from a local network. That's why I need it, in case I'm upstairs and need to start the computer from afar. I don't use it to prevent it from hibernating, or whatever it is called. I would just want the screen to go black after some inactivity. Is that not compatible with having WOL on ?
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NaomiJOSep 15 '12 at 22:23